Machine Tapping Large Bore Nuts with Torque Monitor & Control

Our customers frequently ask for our advice to improve operations and 30% increase in shift production for a tapping operation.

The original machine used reversing motor contactors to electrically reverse the spindle motor for tapping, then reversing out of the tapped part.  This allowed the motor to draw peak current, on each start of the motor. There was no limiting of monitoring of the motor current/torque as the tap became dull.

Sharpening the tap is inexpensive compared to the cost of a brand new tap. A broken tap would force lost production while the tap was removed from the part.

In our design, we selected three methods of motor control.

  1. Ramp accel/decel of the motor/spindle
  2. Limit the maximum torque supplied to the motor
  3. Monitor the actual current draw of the motor
  4. Controlling the accel/decel through the VFD (variable frequency drive) dramatically reduced the motor heating on forward/reverse transitions.  It also eliminated the slamming of the reversing motion.

Controlling the current/torque limit has several advantages:

  1. Stop the motor, if necessary, before a tap breaks,
  2. Eliminate the slug of energy, which shortened life of the other machine components.
  3. Monitoring the current/torque allowed the operator to be alerted that the tap life was nearly completed. The operator would replace the tap with a sharp tap and continue operation,

Performance and Cost Benefits

  1. Eliminate cost of Broken taps
  2. Eliminate downtime of broken taps in parts
  3. Improve operators skill with dull tap alert